Disclosed is system and method for measuring the tension of a tennis net, and, alternatively or in addition, for determining if a service let occurs via the measuring of the net tension. The disclosed embodiments measure a force exerted on the center-strap or the singles stick by the net. In these embodiments, the measured force provides an accurate reflection of the tension of the net.

Disclosed is a method of playing a game. The method comprising providing a hexagon-shaped playing field with six boundary lines. Further, the method comprising providing a ball having the spherical shape similar to that of an American basketball. Further, the method comprising providing three baskets attached to three backboards attached to three poles, wherein each basket in the three baskets includes a net attached to a hoop, wherein each pole in the three poles is installed at three boundary lines in the six boundary lines respectively, wherein the three boundary lines are unconnected from each other. Further, the method comprising providing three teams of players comprising a first team of players associated with a first basket in the three baskets, a second team of players associated with a second basket in the three baskets and a third team of players associated with a third basket in the three baskets.

A variable-color region (886) extending to an exposed surface (102) at a surface zone (892) having a boundary (1212 or 1214) responds to an object (104) impacting the zone sufficiently hard to meet threshold impact criteria at an object-contact area (896) by changing color at a corresponding print area (898) or by providing an impact signal that causes color change at the print area if supplemental impact criteria are also met. In either case, a smoothened image of the print area is produced by determining a portion of the boundary where the print area is nearest the boundary, approximating at least that boundary portion as a smooth boundary vicinity curve, approximating the print area's perimeter, or a portion thereof nearest the boundary, as a smooth perimeter vicinity curve, and comparing the vicinity curves to determine if they meet or overlap.

Disclosed is system and method for measuring the tension of a tennis net, and, alternatively or in addition, for determining if a service let occurs via the measuring of the net tension. The disclosed embodiments measure a force exerted on the center-strap or the singles stick by the net. In these embodiments, the measured force provides an accurate reflection of the tension of the net.

An exercise assist tool is used together with an exercise tool used in a supine or seated state, and the exercise assist tool includes a body-axis indicator that allows a user to be conscious of a body axis. The body-axis indicator has a longitudinal direction, and is supported such that the longitudinal direction can be disposed along a craniocaudal axis of the user. The body-axis indicator is a rod member supported so as to be disposed along a craniocaudal axis of the user. The body-axis indicator includes a proximal-side indicator provided in front of a face of the user, and a distal-side indicator provided farther from the user than the proximal-side indicator. The proximal-side indicator is configured to be capable of adjusting a distance from the user.

A tackle training system defines a frame configured for attachment to a player's body. The frame has an upper portion, a lower portion, and a center portion extending therebetween. The upper portion defines at least one attachment structure extending downwardly toward the lower portion, and the lower portion defines at least one attachment structure extending upwardly toward the upper portion generally vertically aligned with the attachment structure of the upper portion. The opposing attachment structures are for contacting opposing ends of a bar so as to removably attach and extend the bar between the upper and lower portions. The attachment structures of the frame limit movement of the removable bar generally to that of the frame and allow release of the removable bar from the frame when a force that overcomes an attachment force provided by the attachment structures is applied to the removable bar.

A variable-color region (106) of an information-presentation structure extends to an exposed surface (102) at a surface zone (112) and normally appears along it as a principal color. An impact-dependent portion (138) of the variable-color region responds to an object (104) impacting the zone at an object-contact area (116) by temporarily emitting light suitable for forming color different from the principal color if the impact meets threshold impact criteria such that the impact-dependent portion temporarily appears along a print area (118) of the zone as changed color materially different from the principal color. The print area closely matches the object-contact area in size, shape, and location. Use of light emission to produce the temporary color change is advantageous because the changed color can be virtually any possible visible color.

A variable-color region (106) of an information-presentation structure extends to an exposed surface (102) at a surface zone (112), normally appears along it as a principal color, and includes impact-sensitive and color-change components (182 and (184). A segment (192) of the impact-sensitive component responds to an object (104) impacting the zone at an object-contact area (116) by providing an impact effect if the impact meets threshold impact criteria. A segment (194) of the color-change component responds to the effect by causing an impact-dependent portion (138) of the variable-color region to temporarily appear along a print area (118) of the zone as changed color materially different from the principal color. The print area closely matches the object-contact area. The object subsequently leaves the object-contact area. The impact-dependent portion first appears as the changed color no more than 0.2 s after the object leaves the object-contact area.

A variable-color region (106) extends to an exposed surface (102) at a zone (112) and normally appears along it as a principal color. The region responds to an object (104) impacting the zone sufficiently hard at an object-contact area (116) by providing an impact signal identifying a criteria-meeting area (1626) where threshold impact criteria are met. Responsive to the impact signal and possibly to supplemental impact criteria being met, a controller (1622) produces a representation of a print area (118) from a representation of the criteria-meeting area by smoothening its perimeter and provides an initiation signal designating a location in the zone for the print area such that it closely matches the object-contact area. An impact-dependent portion (138) of the region responds to the initiation signal and possibly to a tracking condition being met by temporarily appearing along the print area as changed color materially different from the principal color.

A variable-color region (106) of an information-presentation structure extends to an exposed surface (102) at a surface zone (112), normally appears along it as a principal color, and includes impact-sensitive color-change structure (132) and protective structure (242) lying at least partly between the zone and the impact-sensitive color-change structure. A segment (142) of the impact-sensitive color-change structure responds to an object (104) impacting the zone at an object-contact area (116) by causing an impact-dependent portion (138) of the variable-color region to temporarily appear, typically via light emission, along a print area (118) of the zone as changed color materially different from the principal color if the impact meets threshold impact criteria. The print area closely matches the object-contact area in size, shape, and location. The protective structure materially protects the impact-sensitive color-change structure from being damaged by matter impacting, situated on, and/or moving along the zone.